Fluorescent symbol display tube having plural cathodes and/or vacuum anode insulation

ABSTRACT

An evacuated glass envelope contains a plurality of selectively energizable phosphor-coated elements (anodes) for presenting a symbol display. One or more thermionic cathodes are situated between the display elements and the display surface of the envelope to provide a direct electron beam to the phosphor-coated surfaces. The dull red glow of the thermionic cathodes is masked by the symbol display itself and, optionally, by a filter covering the display surface of the envelope. Variations in intensity at the end portions of the display elements are prevented by eliminating insulating members which would accumulate a charge tending to repel the electron beam. Optionally, the end portions of the display elements may be extended and curved to overlap one another and thus provide a symbol display formed by an unbroken luminous field.

United States Patent Raago Aug. 29, 1972 [54] FLUORESCENT SYMBOL DISPLAY 3,201,634 8/1965 Weidel et al ..313/ 109.5 X

TUBE HAVING PLURAL CATHODES AND/0R VACUUM ANODE FOREIGN PATENTS OR APPLICATIONS INSULATION 11,865 5/1964 Japan ..313/108 [72] Inventor: 0 Raago, Momstown, NJ. Primary Examiner Roy Lake Assistant Examiner-Palmer C. Demeo [73] Assignee: Wagner Electric Corporation Attorney-Eyre, Mann & Lucas [22] Filed: Aug. 24, 1970 [57] ABSTRACT PP ,403 An evacuated glass envelope contains a plurality of selectively energizable phosphor-coated elements Related Apphcatlon Data (anodes) for presenting a symbol display. One or more [63] Continuation-in-part of Ser. No. 751,168, Aug. thermionic cathodes are situated between the display 8, 1968, abandoned. elements and the display surface of the envelope to provide a direct electron beam to the phosphor-coated [52] US. Cl. ..313/l08 R, 313/ 109.5, 313/112, surfaces. The dull red glow of the thermionic cathodes 313/217 is masked by the symbol'display itself and, optionally, [51] Int. Cl. ..H01j 1/88, H0 1 j 63/00 by a filter covering the display surface of the em [58] Field of Search ..313/109.5, 108 R, 217, 112; velope.

ads/169R Variations in intensity at the end portions of the display elements are prevented by eliminating insulating [56] References Clted members which would accumulate a charge tending to UNITED STATES PATENTS repelthe electron beam. Optionally, the end portions of the display elements may be extended and curved 3509402 4/1970 P et ""313/1095 to overlap one another and thus provide a symbol dis- Tanjl formed an unbroken luminous field 3,553,525 l/1971 McGuirk, Jr. ..313/109 .5 X 2,957,098 lO/l960 Bernstein ..3l3/109.5 X 12 Claims, 5 Drawing Figures 3,067,355 12/1962 McCauley ..313/1 12 X 3,136,911 6/1964 Crawford et ...313/109.5 X

FLUORESCENT SYMBOL DISPLAY TUBE HAVING PLURAL CATHODES AND/R VACUUM ANODE INSULATION The present application is a continuation-in-part of application Ser. No. 751,168 filed on Aug. 8, 1968 by Rein Raago, and now abandoned.

The present invention relates to an improved and greatly simplified symbol display device. Specifically, the invention employs a number of phosphor-coated, selectively energizable anodes mounted in an evacuated glass envelope with one or more thermionic cathodes positioned between the anodes and the display surface of the envelope.

The prior art includes, inter alia, neon lamps and evacuated lamps with phosphorescent anodes being bombarded by an electron stream which must be bent in order to provide an adequate display. In the latter type of device, the source of the electron stream is situated behind the display elements, i.e., out of the line of sight of the viewer. This arrangement necessitated a severe deflection of the electron stream to turn the electrons in the opposite direction with an accompanying loss in the kinetic energy in the individual electrons in the stream. Thus, this class of devices does not make the most economical use of the supplied power. The present device, however, requires no such sudden changes in direction of the electron stream and thus imparts to each electron in the stream a higher kinetic energy for any given power input to the tube. Sufficient kinetic energy to render an anode display element luminescent may be imparted to the electrons in the stream over a distance which is relatively short as compared to the prior art devices, since deflection of the electrons is minimized. In addition, the masks, control grids, accelerating grids, anode insulators, etc., all of which are to be found in the prior art devices and all of which contribute to the degradation of the symbol display, have been eliminated. The devices embodying the present invention utilize two or more cathodes positioned in relation to one another so that the electron stream emanating from each cathode causes lateral deflection of the electron stream(s) emanating from the other cathode(s). Consequently, there is no need for a space charge grid to effect beam-spreading, which is necessary to produce a symbol display of uniform intensity. Thus, applicant has devised a simpler, more rugged, more efficient and more economical display device than any to be found in the prior art.

Though it would naturally be assumed that the glow of the thermionic cathode in the line of sight of the viewer would have a deleterious effect on the symbol display, this has been found not to be so. Rather, the dull red glow of the cathodes has been found to be either completely masked by the luminescence of the display elements, or if not so masked, the glow can be eliminated by the use of a bluegreen filter on the display surface of the envelope. In either case, there is no interference from the glow of the cathode with the symbol displays formed by the tube, and this is a very important feature of the construction and operation of a display tube embodying the present invention.

Another advantage of the disclosed embodiment of the invention lies in the positioning of the anode display elements in close proximity to the interior surface of the base portion of the envelope, this disposition being made possible by placement of the cathode(s) between the display surface and the anode display elements. Each of the anode display elements is mounted on a single connector extending through the base portion, thus providing a cantilever-type mount for each element. By keeping the length of the cantilevers as small as possible, great rigidity in mounting the anode display elements is attainable since flexing of the cantilevers is minimized. This high degree of rigidity affords the further advantage of obviating the need for insulating elements to be rigidly connected between the end portions of the anode display elements. In the present invention, the only insulator is the vacuum within the tube separating the aforementioned end portions of the display elements. Since the mass of the cathode(s) is relatively low compared to the mass of even a single anode display element, the cathode(s) are more suitably mounted between longer connectors. There is, of course, the incidental saving in materials through the use of seven relatively short connectors and two relatively long connectors, rather than seven relatively long connectors and two relatively short connectors as in a tube in which the cathode(s) are mounted behind the anode display elements. Finally, the extremely short cantilevered mounting of the anode display elements imparts a high degree of ruggedness to the device.

A highly advantageous and unexpected result has been found to flow from the elimination of insulating members from the spaces between adjacent end portions of the display elements. Specifically, in display tubes which employ insulators to interconnect the end portions of the anode display elements, it has been ob served that the intensity of luminescence of these end portions was uneven and of a generally lower level than the remainder of the elements. This phenomenon is particularly severe in low-voltage devices such as those disclosed in the present application. Removal of the insulators eliminated this undesirable effect. The best analysis of this phenomenon is that the insulators accumulated and held a charge as a result of bombardment by the electron stream. As a result of this accumulated charge, those electrons in the electron stream which would normally strike the end portions of the anode display elements were either repelled from these end portions and thus did not strike the phosphor coating at all, or if they were not sufficiently repelled to miss completely, they struck the phosphor coating with decreased kinetic energy. Thus, as observed, the end portions of the anode display elements had a lower intensity of luminescence than the main or central portion of the anode display elements. This deleterious effect is sometimes referred to as dog-boning, and is completely obviated by the elimination of insulating elements between the end portions of the anode display elements.

The present invention optionally incorporates the novel feature of overlapping luminescent display elements, which results in the formation of the symbol display by an unbroken luminous field. The prior art devices characteristically formed a discontinuous numerical or alphabetical display by various combinations of discrete stick elements which were separated by non-luminescent insulators between the ends of these stick elements. By overlapping the elements of the display, the applicant provides a continuously formed symbol display which is more rapidly recognizable than the prior art displays.

A more complete understanding of the present invention may be obtained by referring to the accompanying drawings, of which:

FIG. 1 is a front view of a display tube constructed in accordance with the present invention and employing a single cathode;

FIG. 2 is a front view of a display tube constructed in accordance with the present invention and employing two cathodes;

FIG. 3 is a front view of a display tube constructed in accordance with the present invention and employing three cathodes;

FIG. 4 is a side view of the display tube of FIG. 1 with the envelope broken away; and

FIG. 5 is an isometric view of the end portions of three display elements forming an overlapping junction.

Referring now specifically to FIG. 1, the display tube may be seen to comprise glass envelope 12 with a cathode 14A substantially vertically and centrally mounted therein in the line of sight of the viewer. Behind the cathode 14 are seven phosphor-coated elements (anodes) forming the display, comprising elements 16A, 16B, 16C, 16D, 16E, 16F, and 16G.

Referring now specifically to FIG. 2, this embodiment is substantially identical to that shown in FIG. 1 with the exception that there are two cathodes 14A and 14B substantially vertical and parallel to one another and situated as to provide an even distribution of high velocity electrons to each of the seven display elements 16A, 16B, 16C, 16D, 16E, 16F and 16G.

Referring now specifically to the embodiment shown in FIG. 3, this embodiment is substantially identical to FIG. 1 with the exception that there are three cathodes 14A, 14B and 14C mounted substantially vertically and parallel to one another so as to provide an even distribution of high velocity electrons to each of the seven display elements 16A, 16B, 16C, 16D, 16E, 16F and 166.

Referring now specifically to the embodiment shown in FIG. 4, the transparent glass envelope 12 may be seen to have a thickened rear or base portion 18. The envelope 12 is of a substantially cylindrical configuration, with a diameter greater than the length along its axis. The number of electrical connectors 20A, 20B, 20C, 20D (behind 20E), 20E, 20F (behind 20G), and 206 are attached to display elements 16A, 16B, 16C, 16D, 16E, 16F and 16G, respectively, and extend through the thickened base portion 18 for connection to a control circuit. The connectors 22 and 24 are attached to the terminals of cathode 14A and extend through the thickened base portion 18 for connection to the source of electrical power. In this view, it may be seen that the end portions of the various anode display elements (except 16B) have a reflex curvature so as to be spaced from one another at their junction when mounted in the envelope 12 by their associated connectors.

Referring now specifically to FIG. 5, the overlapping ends of display elements 16D, 16B, and 16F are shown in the front isometric view. It may be seen that the end portions of display elements 16D and 16F are curved away from one another so as to provide sufficient space for the intrusion of the end portion of display element 168 therebetween. The various elements are insulated from one another exclusively by the vacuum within envelope 12.

In summary, applicant has devised a symbol display tube having a very simple physical structure which affords great economies in cost of materials and fabrication. This device makes highly efiicient use of the applied power by minimizing the deflection of the electron strearn(s). This device is highly compact as a result of the placement of the electron source(s). Elimination of anode insulators prevents dog-boning. Finally, the display may be formed by a continuous luminous field, rather than by discrete stick elements, to be made more easily readable.

The advantages of the present invention will be apparent to those skilled in the art, as well as changes which could be made in the foregoing embodiments without departing from the spirit and scope of the invention. For example, instead of utilizing an envelope the base portion of which is substantially parallel to the planes of the display elements and the display surface, i.e., a vertical base, an envelope in which the base portion is substantially perpendicular to the display elements and display surface, i.e., a horizontal base, could readily be employed. Also, instead of utilizing two or more discrete parallel cathodes, a single, continuous cathode element having two or more portions thereof similarly arrayed could be advantageously utilized. Also, instead of arranging either the discrete cathodes or sections of a continuous cathode in parallel, a V- shaped (two cathodes or cathode segments) or N- shaped (three cathodes or cathode segments) array could be advantageously employed. With such arrays, the mutual repelling forces would be greater in the region where the cathodes or cathode segments are in close proximity and weaker in the region where they are farther apart, thus effecting spreading of the electron streams to the degree required by the spacing at any particular level of the display. It will be readily apparent that, in the aforementioned embodiment employing a single, continuous cathode wire, a break in that cathode wire will effectively disable the source of the electron strea.m(s). In many applications, it is far more hazardous to have an erroneous readout, which might occur if one of several discrete cathodes failed, than it would be to have no readout at all. In the latter situation, an observer will at least know that the display tube is not functioning, whereas with an erroneous readout, an'observer would have no reason to believe that there is a display tube malfunction.

Therefore, it should be understood that the present invention is not to be limited to the foregoing description of the specific embodiments thereof, but is to be determined by the spirit and scope of the accompanying claims.

What is claimed is:

1. A display tube comprising:

1. an evacuated transparent envelope having a display surface and a base portion;

2. a plurality of anode display elements each of which is at least partially coated with a phosphor, all disposed within said transparent envelope so as to form any of a desired group of symbols by selectively energizing said anode display elements;

3. at least two cathodes disposed between said display surface and said plurality of anode display elements and positioned in relation to one another so as to cause mutual lateral deflection of the electron streams emanating from said cathodes; and

4. a plurality of means operative to support said anode display elements and said at least two cathodes, and to electrically connect said anode display elements and said at least two cathodes to external circuitry.

2. A display tube according to claim 1 wherein said at least two cathodes are substantially vertically disposed with respect to said plurality of anode display elements.

3. A display tube according to claim 1 wherein said cathodes are substantially parallel to one another.

4. A display tube according to claim 1 wherein filter means operative to mask the glow of said at least two cathodes is disposed on said display surface of said transparent envelope.

5. A display tube according to claim 1 wherein said plurality of anode display elements overlap at each junction of two or more of said anode display elements so as to form any desired display with a continuous luminous field.

6. A display tube according to claim 5 wherein, at each junction of two or more of said anode display elements, at least one of said anode display elements has a reflex curvature in the end portion at the junction.

7. A display tube comprising:

1. an evacuated transparent envelope having a display surface and a base portion;

2. a plurality of anode display elements each of which is at least partially coated with a phosphor, the adjacent end portions of which are insulated from one another exclusively by the vacuum within said transparent envelope, said anode display elements being disposed within said transparent envelope to form any one of a predetermined group of symbols by selective energization of said anode display elements;

. at least one cathode disposed between said display surface and said plurality of anode display elements; and

4. a plurality of means operative to support said anode display elements and said at least one cathode, and to electrically connect said anode display elements and said at least one cathode to external circuitry.

8. A display tube according to claim 7 wherein said plurality of anode display elements overlap at each junction of two or more of said anode display elements so as to form any desired display with a continuous luminous field.

9. A display tube according to claim 8 wherein, at each junction of two or more of said anode display elements, at least one of said anode display elements has a reflex curvature in the end portion at the junction.

10. A gridless display tube comprising:

1. an evacuated transparent envelope having a display surface and a base portion;

2. a plurality of anode display elements each of which is at least partially coated with a phosphor, all disposed within said transparent envelope so as to form any of a desired group of symbols by selectively energizing said anode display elements;

3. at least two cathodes disposed between said display surface and said plurality of anode display elements and positioned in relation to one another so as to cause mutual lateral deflection of the electron stre s emanating from said cathodes; and 4. a plur ity of means operative to support said 

1. A display tube comprising:
 1. an evacuated transparent envelope having a display surface and a base portion;
 2. a plurality of anode display elements each of which is at least partially coated with a phosphor, all disposed within said transparent envelope so as to form any of a desired group of symbols by selectively energizing said anode display elements;
 3. at least two cathodes disposed between said display surface and said plurality of anode display elements and positioned in relation to one another so as to cause mutual lateral deflection of the electron streams emanating from said cathodes; and
 4. a plurality of means operative to support said anode display elements and said at least two cathodes, and to electrically connect said anode display elements and said at least two cathodes to external circuitry.
 2. A display tube according to claim 1 wherein said at least two cathodes are substantially vertically disposed with respect to said plurality of anode display elements.
 2. a plurality of anode display elements each of which is at least partially coated with a phosphor, all disposed within said transparent envelope so as to form any of a desired group of symbols by selectively energizing said anode display elements;
 2. a plurality of anode display elements each of which is at least partially coated with a phosphor, the adjacent end portions of which are insulated from one another exclusively by the vacuum within said transparent envelope, said anode display elements being disposed within said transparent envelope to form any one of a predetermined group of symbols by selective energization of said anode display elements;
 2. a plurality of anode display elements each of which is at least partially coated with a phosphor, all disposed within said transparent envelope so as to form any of a desired group of symbols by selectively energizing said anode display elements;
 3. at least two cathodes disposed between said display surface and said plurality of anode display elements and positioned in relation to one another so as to cause mutual lateral deflection of the electron streams emanating from said cathodes; and
 3. at least one cathode disposed between said display surface and said plurality of anode display elements; and
 3. at least two cathodes disposed between said display surface and said plurality of anode display elements and positioned in relation to one another so as to cause mutual lateral deflection of the electron streams emanating from said cathodes; and
 3. A display tube according to claim 1 wherein said cathodes are substantially parallel to one another.
 4. A display tube according to claim 1 wherein filter means operative to mask the glow of said at least two cathodes is disposed on said display surface of said transparent envelope.
 4. a plurality of means operative to support said anode display elements and said at least two cathodes, and to electrically connect said anode display elements and said at least two cathodes to external circuitry.
 4. a plurality of means operative to support said anode display elements and said at least one cathode, and to electrically connect said anode display elements and said at least one cathode to external circuitry.
 4. a plurality of means operative to support said anode display elements and said at least two cathodes, and to electrically connect said anode display elements and said at least two cathodes to external circuitry.
 5. A display tube according to claim 1 wherein said plurality of anode display elements overlap at each junction of two or more of said anode display elements so as to form any dEsired display with a continuous luminous field.
 6. A display tube according to claim 5 wherein, at each junction of two or more of said anode display elements, at least one of said anode display elements has a reflex curvature in the end portion at the junction.
 7. A display tube comprising:
 8. A display tube according to claim 7 wherein said plurality of anode display elements overlap at each junction of two or more of said anode display elements so as to form any desired display with a continuous luminous field.
 9. A display tube according to claim 8 wherein, at each junction of two or more of said anode display elements, at least one of said anode display elements has a reflex curvature in the end portion at the junction.
 10. A gridless display tube comprising:
 11. A display tube according to claim 10 wherein said at least two cathodes are substantially vertically disposed with respect to said plurality of anode display elements.
 12. A display tube according to claim 10 wherein said cathodes are substantially parallel to one another. 